John Mousinho lamented Pompey’s performance in the first half of their final fixture of the calendar year.
They created little at Exeter and it took a triple substitution after the break before the visitors were able to pose a sustained attacking threat.
But they could not convert any of those chances as the Devon contest finished in a goalless stalemate.
And Mousinho knows his side have to produce more consistent displays in order to maintain their position at the top of the League One table.
The Blues boss said: “It’s obviously frustrating and I felt that we wasted most of the first 45 minutes after starting well.
“But we lost control and didn’t do anything particularly well – you can’t just hope that things will get better after the break.
"It’s obviously frustrating and I felt that we wasted most of the first 45 minutes after starting well."
“We were the team in the ascendency from then on and had a few chances that on another day, we put in the back of the net.
“That performance was fine, but when you waste a half like we did, you leave yourself open to not winning.
“If we’d have beaten Fleetwood and got the result we deserved at Bristol Rovers, then you put it down to an off night, take the point and move on.
“The frustration builds because of the past two games, so now we have to address some of those issues.
“To get to 50 points at this stage of the season is a big achievement, but there’s a lot for us still to improve on.
“There’s only a couple of days for us to get ready to face Stevenage and we’ll try to put in a good performance on Monday.”